/*
 * Copyright (c) 2016-present, Yann Collet, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under both the BSD-style license (found in the
 * LICENSE file in the root directory of this source tree) and the GPLv2 (found
 * in the COPYING file in the root directory of this source tree).
 * You may select, at your option, one of the above-listed licenses.
 */

/* zstd_decompress_internal:
 * objects and definitions shared within lib/decompress modules */

#ifndef ZSTD_DECOMPRESS_INTERNAL_H
#define ZSTD_DECOMPRESS_INTERNAL_H

/*-*******************************************************
 *  Dependencies
 *********************************************************/
#include "mem.h"           /* BYTE, U16, U32 */
#include "zstd_internal.h" /* ZSTD_seqSymbol */

/*-*******************************************************
 *  Constants
 *********************************************************/
static const U32 LL_base[MaxLL + 1] = {
    0,  1,  2,  3,  4,  5,  6,  7,  8,    9,     10,    11,    12,    13,     14,     15,     16,     18,
    20, 22, 24, 28, 32, 40, 48, 64, 0x80, 0x100, 0x200, 0x400, 0x800, 0x1000, 0x2000, 0x4000, 0x8000, 0x10000};

static const U32 OF_base[MaxOff + 1] = {0,         1,          1,          5,         0xD,       0x1D,      0x3D,
                                        0x7D,      0xFD,       0x1FD,      0x3FD,     0x7FD,     0xFFD,     0x1FFD,
                                        0x3FFD,    0x7FFD,     0xFFFD,     0x1FFFD,   0x3FFFD,   0x7FFFD,   0xFFFFD,
                                        0x1FFFFD,  0x3FFFFD,   0x7FFFFD,   0xFFFFFD,  0x1FFFFFD, 0x3FFFFFD, 0x7FFFFFD,
                                        0xFFFFFFD, 0x1FFFFFFD, 0x3FFFFFFD, 0x7FFFFFFD};

static const U32 OF_bits[MaxOff + 1] = {0,  1,  2,  3,  4,  5,  6,  7,  8,  9,  10, 11, 12, 13, 14, 15,
                                        16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31};

static const U32 ML_base[MaxML + 1] = {
    3,  4,  5,  6,  7,  8,  9,  10,   11,    12,    13,    14,    15,     16,     17,     18,     19,     20,
    21, 22, 23, 24, 25, 26, 27, 28,   29,    30,    31,    32,    33,     34,     35,     37,     39,     41,
    43, 47, 51, 59, 67, 83, 99, 0x83, 0x103, 0x203, 0x403, 0x803, 0x1003, 0x2003, 0x4003, 0x8003, 0x10003};

/*-*******************************************************
 *  Decompression types
 *********************************************************/
typedef struct {
    U32 fastMode;
    U32 tableLog;
} ZSTD_seqSymbol_header;

typedef struct {
    U16 nextState;
    BYTE nbAdditionalBits;
    BYTE nbBits;
    U32 baseValue;
} ZSTD_seqSymbol;

#define SEQSYMBOL_TABLE_SIZE(log) (1 + (1 << (log)))

typedef struct {
    ZSTD_seqSymbol LLTable[SEQSYMBOL_TABLE_SIZE(LLFSELog)]; /* Note : Space reserved for FSE Tables */
    ZSTD_seqSymbol OFTable[SEQSYMBOL_TABLE_SIZE(
        OffFSELog)]; /* is also used as temporary workspace while building hufTable during DDict creation */
    ZSTD_seqSymbol MLTable[SEQSYMBOL_TABLE_SIZE(
        MLFSELog)]; /* and therefore must be at least HUF_DECOMPRESS_WORKSPACE_SIZE large */
    HUF_DTable hufTable[HUF_DTABLE_SIZE(HufLog)]; /* can accommodate HUF_decompress4X */
    U32 rep[ZSTD_REP_NUM];
} ZSTD_entropyDTables_t;

typedef enum {
    ZSTDds_getFrameHeaderSize,
    ZSTDds_decodeFrameHeader,
    ZSTDds_decodeBlockHeader,
    ZSTDds_decompressBlock,
    ZSTDds_decompressLastBlock,
    ZSTDds_checkChecksum,
    ZSTDds_decodeSkippableHeader,
    ZSTDds_skipFrame
} ZSTD_dStage;

typedef enum { zdss_init = 0, zdss_loadHeader, zdss_read, zdss_load, zdss_flush } ZSTD_dStreamStage;

typedef enum {
    ZSTD_use_indefinitely = -1, /* Use the dictionary indefinitely */
    ZSTD_dont_use = 0,          /* Do not use the dictionary (if one exists free it) */
    ZSTD_use_once = 1           /* Use the dictionary once and set to ZSTD_dont_use */
} ZSTD_dictUses_e;

struct ZSTD_DCtx_s {
    const ZSTD_seqSymbol* LLTptr;
    const ZSTD_seqSymbol* MLTptr;
    const ZSTD_seqSymbol* OFTptr;
    const HUF_DTable* HUFptr;
    ZSTD_entropyDTables_t entropy;
    U32 workspace[HUF_DECOMPRESS_WORKSPACE_SIZE_U32]; /* space needed when building huffman tables */
    const void* previousDstEnd;                       /* detect continuity */
    const void* prefixStart;                          /* start of current segment */
    const void* virtualStart; /* virtual start of previous segment if it was just before current one */
    const void* dictEnd;      /* end of previous segment */
    size_t expected;
    ZSTD_frameHeader fParams;
    U64 decodedSize;
    blockType_e bType; /* used in ZSTD_decompressContinue(), store blockType between block header decoding and block
                          decompression stages */
    ZSTD_dStage stage;
    U32 litEntropy;
    U32 fseEntropy;
    XXH64_state_t xxhState;
    size_t headerSize;
    ZSTD_format_e format;
    const BYTE* litPtr;
    ZSTD_customMem customMem;
    size_t litSize;
    size_t rleSize;
    size_t staticSize;
    int bmi2; /* == 1 if the CPU supports BMI2 and 0 otherwise. CPU support is determined dynamically once per context
                 lifetime. */

    /* dictionary */
    ZSTD_DDict* ddictLocal;
    const ZSTD_DDict* ddict; /* set by ZSTD_initDStream_usingDDict(), or ZSTD_DCtx_refDDict() */
    U32 dictID;
    int ddictIsCold; /* if == 1 : dictionary is "new" for working context, and presumed "cold" (not in cpu cache) */
    ZSTD_dictUses_e dictUses;

    /* streaming */
    ZSTD_dStreamStage streamStage;
    char* inBuff;
    size_t inBuffSize;
    size_t inPos;
    size_t maxWindowSize;
    char* outBuff;
    size_t outBuffSize;
    size_t outStart;
    size_t outEnd;
    size_t lhSize;
    void* legacyContext;
    U32 previousLegacyVersion;
    U32 legacyVersion;
    U32 hostageByte;
    int noForwardProgress;

    /* workspace */
    BYTE litBuffer[ZSTD_BLOCKSIZE_MAX + WILDCOPY_OVERLENGTH];
    BYTE headerBuffer[ZSTD_FRAMEHEADERSIZE_MAX];
}; /* typedef'd to ZSTD_DCtx within "zstd.h" */

/*-*******************************************************
 *  Shared internal functions
 *********************************************************/

/*! ZSTD_loadDEntropy() :
 *  dict : must point at beginning of a valid zstd dictionary.
 * @return : size of entropy tables read */
size_t ZSTD_loadDEntropy(ZSTD_entropyDTables_t* entropy, const void* const dict, size_t const dictSize);

/*! ZSTD_checkContinuity() :
 *  check if next `dst` follows previous position, where decompression ended.
 *  If yes, do nothing (continue on current segment).
 *  If not, classify previous segment as "external dictionary", and start a new segment.
 *  This function cannot fail. */
void ZSTD_checkContinuity(ZSTD_DCtx* dctx, const void* dst);

#endif /* ZSTD_DECOMPRESS_INTERNAL_H */
